This invention relates to control of analog MEMS arrays and more particularly to analog voltage control of light modulator arrays.
Light modulator arrays using binary digital control of each pixel cell have found applications in monochrome text displays and projectors. In order to produce grayscale and color, it is desirable to control each pixel cell with analog signals rather than simple binary control. For achieving high resolution color or grayscale in light-modulator array systems, two methods commonly considered are pulse-width modulation and direct analog control of modulator elements. Using pulse-width modulation requires separating a single frame cycle into multiple cycle segments and sending data for each modulator element during each cycle segment. For large arrays and high resolution, this can require very high data rates. In the light projector industry, significant effort has been expended towards the goal of finding a means to decrease these data rates while maintaining a desired color resolution. For an array of MEMS devices such as light modulation elements (e.g., micro-mirrors, diffraction-based modulators or interference-based modulators), or of LCD modulators, analog control of the voltage driving the modulator may also be desired to produce grayscale and color. Putting full analog control under each cell of the array can negatively affect light modulation system performance and/or cost. Analog circuitry is area-expensive in integrated circuit processes, and analog control of individual cells may require an increase in cell size, resulting in a decrease in spatial resolution of the modulator array. In an effort to maintain cell size, a fabrication process with higher lithographic resolution and smaller feature sizes may be used, resulting in higher costs. Reliability may also be negatively affected by replication of analog control circuitry at every pixel cell of a light-modulator array.